The present invention relates generally to sterilizers and, more particularly, to a sterilizer having control means for automatically controlling a sterilization process.
Sterilizers are widely used to sterilize articles in medical environments and typically employ a steam filled chamber for containing the article and means for increasing the temperature and pressure inside the chamber to a point where the article is sterilized.
Sterilizers may be used to sterilize either solid or liquid articles and, in a typical sterilization cycle for solid articles, the articles are sealed within a chamber of the sterilizer and steam may be supplied to the chamber. The steam may either be provided by means of a separate steam producing chamber or by supplying water to the chamber and heating the chamber until the water evaporates. In either case, the chamber is provided with a heater to elevate the temperature in the chamber and cause an accompanying increase in pressure such that sterilization of the articles is effected. Further, the presence of steam in the chamber facilitates an increase in pressure therein whereby the temperature and time required for completing the sterilization process may be kept to a minimum.
At the conclusion of the sterilization cycle, the steam in the chamber may be exhausted to a water reservoir where the steam is condensed for reuse in a subsequent cycle. The sterilizer disclosed in U.S. Pat. No. 3,351,422 to Jones et al is typical of such a sterilizer design and includes conduits for conveying water from a reservoir to a sterilization chamber and for conveying steam formed in the chamber back to the reservoir. The reservoir of the Jones et al patent has an open top which allows access to view the water level in the reservoir and to fill the reservoir when necessary. Such an arrangement is subject to a certain amount of evaporation and loss of water from the sterilizer system as steam condenses and exits from the condensing coil and comes into contact with the air above the reservoir water.
Personnel operating the sterilizer typically release additional steam from the sterilizer chamber by opening the sterilizer door after the pressure within the chamber has been reduced to a level near atmospheric pressure and before the articles in the chamber have cooled, such that any moisture remaining on the articles is caused to evaporate more quickly as the moisture content of the chamber decreases. By including this step in the sterilization cycle, the time required for the chamber and the article contained therein to reach a reduced temperature is decreased. Further the elevated temperature of the articles at the time when the door is opened insures that the articles will be completely dry when they are cool enough to be removed from the chamber.
The above cooling and drying step of the sterilization cycle is typically facilitated by a timer which sounds an audible warning signal when the pressure in the chamber has reached a safe level for the door to be opened. Obviously, this step requires that a person be in attendance near the chamber as the sterilization cycle is nearing completion in order for the chamber to be opened prior to the temperature of the articles decreasing to a point where the moisture will no longer evaporate from them. The door opening step may only be completed after the pressure within the chamber has been significantly reduced to avoid the possibility of the pressurized gases within the chamber causing the door to spring open and strike the operator.
Accordingly, there is a need for a sterilizing apparatus which may be operated automatically with a minimum of supervision from operating personnel and which incorporates a door opening step in its sterilization cycles. Further, there is a need for a sterilizing apparatus which automatically opens its door a controlled amount at the conclusion of sterilization cycles.
In addition, there is a need for a sterilizing apparatus which efficiently controls the recovery of steam within the water reservoir such that a minimum of steam is lost during the sterilization cycles.